/*
 * Copyright 2014 The Netty Project
 *
 * The Netty Project licenses this file to you under the Apache License,
 * version 2.0 (the "License"); you may not use this file except in compliance
 * with the License. You may obtain a copy of the License at:
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations
 * under the License.
 */

package io.netty.util;

import io.netty.util.internal.StringUtil;

import java.net.IDN;
import java.util.Collections;
import java.util.LinkedHashMap;
import java.util.Locale;
import java.util.Map;

import static io.netty.util.internal.ObjectUtil.checkNotNull;
import static io.netty.util.internal.StringUtil.commonSuffixOfLength;

/**
 * Maps a domain name to its associated value object.
 * <p>
 * DNS wildcard is supported as hostname, so you can use {@code *.netty.io} to match both {@code
 * netty.io} and {@code downloads.netty.io}.
 * </p>
 */
public class DomainNameMapping<V> implements Mapping<String, V> {

  final V defaultValue;
  private final Map<String, V> map;
  private final Map<String, V> unmodifiableMap;

  /**
   * Creates a default, order-sensitive mapping. If your hostnames are in conflict, the mapping will
   * choose the one you add first.
   *
   * @param defaultValue the default value for {@link #map(String)} to return when nothing matches
   * the input
   * @deprecated use {@link DomainNameMappingBuilder} to create and fill the mapping instead
   */
  @Deprecated
  public DomainNameMapping(V defaultValue) {
    this(4, defaultValue);
  }

  /**
   * Creates a default, order-sensitive mapping. If your hostnames are in conflict, the mapping will
   * choose the one you add first.
   *
   * @param initialCapacity initial capacity for the internal map
   * @param defaultValue the default value for {@link #map(String)} to return when nothing matches
   * the input
   * @deprecated use {@link DomainNameMappingBuilder} to create and fill the mapping instead
   */
  @Deprecated
  public DomainNameMapping(int initialCapacity, V defaultValue) {
    this(new LinkedHashMap<String, V>(initialCapacity), defaultValue);
  }

  DomainNameMapping(Map<String, V> map, V defaultValue) {
    this.defaultValue = checkNotNull(defaultValue, "defaultValue");
    this.map = map;
    unmodifiableMap = map != null ? Collections.unmodifiableMap(map)
        : null;
  }

  /**
   * Adds a mapping that maps the specified (optionally wildcard) host name to the specified output
   * value.
   * <p>
   * <a href="http://en.wikipedia.org/wiki/Wildcard_DNS_record">DNS wildcard</a> is supported as
   * hostname. For example, you can use {@code *.netty.io} to match {@code netty.io} and {@code
   * downloads.netty.io}.
   * </p>
   *
   * @param hostname the host name (optionally wildcard)
   * @param output the output value that will be returned by {@link #map(String)} when the specified
   * host name matches the specified input host name
   * @deprecated use {@link DomainNameMappingBuilder} to create and fill the mapping instead
   */
  @Deprecated
  public DomainNameMapping<V> add(String hostname, V output) {
    map.put(normalizeHostname(checkNotNull(hostname, "hostname")), checkNotNull(output, "output"));
    return this;
  }

  /**
   * Simple function to match <a href="http://en.wikipedia.org/wiki/Wildcard_DNS_record">DNS
   * wildcard</a>.
   */
  static boolean matches(String template, String hostName) {
    if (template.startsWith("*.")) {
      return template.regionMatches(2, hostName, 0, hostName.length())
          || commonSuffixOfLength(hostName, template, template.length() - 1);
    }
    return template.equals(hostName);
  }

  /**
   * IDNA ASCII conversion and case normalization
   */
  static String normalizeHostname(String hostname) {
    if (needsNormalization(hostname)) {
      hostname = IDN.toASCII(hostname, IDN.ALLOW_UNASSIGNED);
    }
    return hostname.toLowerCase(Locale.US);
  }

  private static boolean needsNormalization(String hostname) {
    final int length = hostname.length();
    for (int i = 0; i < length; i++) {
      int c = hostname.charAt(i);
      if (c > 0x7F) {
        return true;
      }
    }
    return false;
  }

  @Override
  public V map(String hostname) {
    if (hostname != null) {
      hostname = normalizeHostname(hostname);

      for (Map.Entry<String, V> entry : map.entrySet()) {
        if (matches(entry.getKey(), hostname)) {
          return entry.getValue();
        }
      }
    }
    return defaultValue;
  }

  /**
   * Returns a read-only {@link Map} of the domain mapping patterns and their associated value
   * objects.
   */
  public Map<String, V> asMap() {
    return unmodifiableMap;
  }

  @Override
  public String toString() {
    return StringUtil.simpleClassName(this) + "(default: " + defaultValue + ", map: " + map + ')';
  }
}
